N'Guessan R

References (15)

Title : Entomological indicators of malaria transmission prior to a cluster-randomized controlled trial of a 'lethal house lure' intervention in central Cte d'Ivoire - Wolie_2022_Malar.J_21_188
Author(s) : Wolie RZ , Koffi AA , Ayuk-Taylor L , Alou LPA , Sternberg ED , N'Nan-Alla O , N'Guessan Y , Dahounto A , Oumbouke WA , Tia IZ , N'Guetta SA , Cook J , Thomas MB , N'Guessan R
Ref : Malar J , 21 :188 , 2022
Abstract : BACKGROUND: A study was conducted prior to implementing a cluster-randomized controlled trial (CRT) of a lethal house lure strategy in central Cote d'Ivoire to provide baseline information on malaria indicators in 40 villages across five health districts. METHODS: Human landing catches (HLC) were performed between November and December 2016, capturing mosquitoes indoors and outdoors between 18.00 and 08.00 h. Mosquitoes were processed for entomological indicators of malaria transmission (human biting, parity, sporozoite, and entomological inoculation rates (EIR)). Species composition and allelic frequencies of kdr-w and ace-1(R) mutations were also investigated within the Anopheles gambiae complex. RESULTS: Overall, 15,632 mosquitoes were captured. Anopheles gambiae sensu lato (s.l.) and Anopheles funestus were the two malaria vectors found during the survey period, with predominance for An. gambiae (66.2%) compared to An. funestus (10.3%). The mean biting rate for An. gambiae was almost five times higher than that for An. funestus (19.8 bites per person per night for An. gambiae vs 4.3 bites per person per night for An. funestus) and this was evident indoors and outdoors. Anopheles funestus was more competent to transmit malaria parasites in the study area, despite relatively lower number tested for sporozoite index (4.14% (63/1521) for An. gambiae vs 8.01% (59/736) for An. funestus; (2) = 12.216; P < 0.0001). There were no significant differences between the proportions infected outdoors and indoors for An. gambiae (4.03 vs 4.13%; (2) = 0.011; P = 0.9197) and for An. funestus (7.89 vs 8.16%; (2) = 2.58(e-29); P = 1). The majority of both infected vectors with malaria parasites harboured Plasmodium falciparum (93.65% for An. gambiae and 98. 31% for An. funestus). Overall, the EIR range for both species in the different districts appeared to be high (0.35-2.20 infected bites per human per night) with the highest value observed in the district of North-Eastern-Bouake. There were no significant differences between transmission occurring outdoor and indoor for both species. Of the An. gambiae s.l. analysed, only An. gambiae sensu stricto (14.1%) and Anopheles coluzzii (85.9%) were found. The allelic frequencies of kdr and ace-1(R) were higher in An. gambiae (0.97 for kdr and 0.19 for ace-1(R)) than in An. coluzzii (0.86 for kdr and 0.10 for ace-1(R)) (P < 0.001). CONCLUSION: Despite universal coverage with long-lasting insecticidal nets (LLINs) in the area, there was an abundance of the malaria vectors (An. gambiae and An. funestus) in the study area in central Cote d'Ivoire. Consistent with high insecticide resistance intensity previously detected in these districts, the current study detected high kdr frequency (> 85%), coupled with high malaria transmission pattern, which could guide the use of Eave tubes in the study areas.
ESTHER : Wolie_2022_Malar.J_21_188
PubMedSearch : Wolie_2022_Malar.J_21_188
PubMedID: 35705981

Title : Fine scale spatial investigation of multiple insecticide resistance and underlying target-site and metabolic mechanisms in Anopheles gambiae in central Cte d'Ivoire - Oumbouke_2020_Sci.Rep_10_15066
Author(s) : Oumbouke WA , Pignatelli P , Barreaux AMG , Tia IZ , Koffi AA , Ahoua Alou LP , Sternberg ED , Thomas MB , Weetman D , N'Guessan R
Ref : Sci Rep , 10 :15066 , 2020
Abstract : Routine monitoring of occurrence, levels and mechanisms of insecticide resistance informs effective management strategies, and should be used to assess the effect of new tools on resistance. As part of a cluster randomised controlled trial evaluating a novel insecticide-based intervention in central Cte d'Ivoire, we assessed resistance and its underlying mechanisms in Anopheles gambiae populations from a subset of trial villages. Resistance to multiple insecticides in An. gambiae s.s. and An. coluzzii was detected across villages, with dose-response assays demonstrating extremely high resistance intensity to the pyrethroid deltamethrin (> 1,500-fold), and mortality following exposure to pyrethroid-treated bednets was low (< 30% mortality in cone bioassays). The 1014F kdr mutation was almost fixed (>= 90%) in all villages but the 1575Y kdr-amplifying mutation was relatively rare (< 15%). The carbamate and organophosphate resistance-associated Ace-1 G119S mutation was also detected at moderate frequencies (22-43%). Transcriptome analysis identified overexpression of P450 genes known to confer pyrethroid resistance (Cyp9K1, Cyp6P3, and Cyp6M2), and also a carboxylesterase (COEAE1F) as major candidates. Cyp6P3 expression was high but variable (up to 33-fold) and correlated positively with deltamethrin resistance intensity across villages (r(2) = 0.78, P = 0.02). Tools and strategies to mitigate the extreme and multiple resistance provided by these mechanisms are required in this area to avoid future control failures.
ESTHER : Oumbouke_2020_Sci.Rep_10_15066
PubMedSearch : Oumbouke_2020_Sci.Rep_10_15066
PubMedID: 32934291

Title : Mapping insecticide resistance in Anopheles gambiae (s.l.) from Cte d'Ivoire - Camara_2018_Parasit.Vectors_11_19
Author(s) : Camara S , Koffi AA , Ahoua Alou LP , Koffi K , Kabran JK , Kone A , Koffi MF , N'Guessan R , Pennetier C
Ref : Parasit Vectors , 11 :19 , 2018
Abstract : BACKGROUND: Insecticide resistance in malaria vectors is an increasing threat to vector control tools currently deployed in endemic countries. Resistance management must be an integral part of National Malaria Control Programmes' (NMCPs) next strategic plans to alleviate the risk of control failure. This obviously will require a clear database on insecticide resistance to support the development of such a plan. The present work gathers original data on insecticide resistance between 2009 and 2015 across Cote d'Ivoire in West Africa. METHODS: Two approaches were adopted to build or update the resistance data in the country. Resistance monitoring was conducted between 2013 and 2015 in 35 sentinel sites across the country using the WHO standard procedure of susceptibility test on adult mosquitoes. Four insecticide families (pyrethroids, organochlorides, carbamates and organophosphates) were tested. In addition to this survey, we also reviewed the literature to assemble existing data on resistance between 2009 and 2015. RESULTS: High resistance levels to pyrethroids, organochlorides and carbamates were widespread in all study sites whereas some Anopheles populations remained susceptible to organophosphates. Three resistance mechanisms were identified, involving high allelic frequencies of kdr L1014F mutation (range = 0.46-1), relatively low frequencies of ace-1 (R) (below 0.5) and elevated activity of insecticide detoxifying enzymes, mainly mixed function oxidases (MFO), esterase and glutathione S-transferase (GST) in almost all study sites. CONCLUSION: This detailed map of resistance highlights the urgent need to develop new vector control tools to complement current long-lasting insecticidal nets (LLINs) although it is yet unclear whether these resistance mechanisms will impact malaria transmission control. Researchers, industry, WHO and stakeholders must urgently join forces to develop alternative tools. By then, NMCPs must strive to develop effective tactics or plans to manage resistance keeping in mind country-specific context and feasibility.
ESTHER : Camara_2018_Parasit.Vectors_11_19
PubMedSearch : Camara_2018_Parasit.Vectors_11_19
PubMedID: 29310704

Title : Re-visiting insecticide resistance status in Anopheles gambiae from Cte d'Ivoire: a nation-wide informative survey - Koffi_2013_PLoS.One_8_e82387
Author(s) : Koffi AA , Ahoua Alou LP , Kabran JP , N'Guessan R , Pennetier C
Ref : PLoS ONE , 8 :e82387 , 2013
Abstract : Insecticide resistance constitutes a major threat that may undermine current gain in malaria control in most endemic countries. National Malaria Control Programmes (NMCPs) need as much information as possible on the resistance status of malaria vectors and underlying mechanisms in order to implement the most relevant and efficient control strategy. Bioassays, biochemical and molecular analysis were performed on An. gambiae collected in six sentinel sites in Cote d'Ivoire. The sites were selected on the basis of their bioclimatic status and agricultural practices. An. gambiae populations across sites showed high levels of resistance to organochloride, pyrethroid and carbamate insecticides. The kdr and ace-1(R) mutations were detected in almost all sentinel sites with mosquitoes on the coastal and cotton growing areas mostly affected by these mutations. At almost all sites, the levels of detoxifying enzymes (mixed-function oxidases (MFOs), non-specific esterases (NSE) and glutathione-S-transferases (GSTs)) in An. gambiae populations were significantly higher than the levels found in the susceptible strain Kisumu. Pre-exposure of mosquitoes to PBO, an inhibitor of MFOs and NSEs, significantly increased mortality rates to pyrethroids and carbamates in mosquitoes but resistance in most cases was not fully synergised by PBO, inferring a residual role of additional mechanisms, including kdr and ace-1 site insensitivity. The large distribution of resistance in Cote d'Ivoire raises an important question of whether to continue to deploy pyrethroid-based long-lasting insecticidal nets (LLINs) and insecticide residual spraying (IRS) towards which resistance continues to rise with no guarantee that the level of resistance would not compromise their efficacy. Innovative strategies that combine insecticide and synergists in LLINs or spatially LLIN and an effective non-pyrethroid insecticide for IRS could be in the short term the best practice for the NMCP to manage insecticide resistance in malaria vectors in Cote d'Ivoire and other endemic countries facing resistance.
ESTHER : Koffi_2013_PLoS.One_8_e82387
PubMedSearch : Koffi_2013_PLoS.One_8_e82387
PubMedID: 24358177

Title : Insecticide resistance status in Anopheles gambiae in southern Benin - Yadouleton_2010_Malar.J_9_83
Author(s) : Yadouleton AW , Padonou G , Asidi A , Moiroux N , Bio-Banganna S , Corbel V , N'Guessan R , Gbenou D , Yacoubou I , Gazard K , Akogbeto MC
Ref : Malar J , 9 :83 , 2010
Abstract : BACKGROUND: The emergence of pyrethroid resistance in Anopheles gambiae has become a serious concern to the future success of malaria control. In Benin, the National Malaria Control Programme has recently planned to scaling up long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) for malaria prevention. It is, therefore, crucial to monitor the level and type of insecticide resistance in An. gambiae, particularly in southern Benin where reduced efficacy of insecticide-treated nets (ITNs) and IRS has previously been reported. METHODS: The protocol was based on mosquito collection during both dry and rainy seasons across forty districts selected in southern Benin. Bioassay were performed on adults collected from the field to assess the susceptibility of malaria vectors to insecticide-impregnated papers (permethrin 0.75%, delthamethrin 0.05%, DDT 4%, and bendiocarb 0.1%) following WHOPES guidelines. The species within An. gambiae complex, molecular form and presence of kdr and ace-1 mutations were determined by PCR. RESULTS: Strong resistance to permethrin and DDT was found in An. gambiae populations from southern Benin, except in Aglangandan where mosquitoes were fully susceptible (mortality 100%) to all insecticides tested. PCR showed the presence of two sub-species of An. gambiae, namely An. gambiae s.s, and Anopheles melas, with a predominance for An. gambiae s.s (98%). The molecular M form of An. gambiae was predominant in southern Benin (97%). The kdr mutation was detected in all districts at various frequency (1% to 95%) whereas the Ace-1 mutation was found at a very low frequency (
ESTHER : Yadouleton_2010_Malar.J_9_83
PubMedSearch : Yadouleton_2010_Malar.J_9_83
PubMedID: 20334637

Title : Indoor use of plastic sheeting impregnated with carbamate combined with long-lasting insecticidal mosquito nets for the control of pyrethroid-resistant malaria vectors - Djenontin_2010_Am.J.Trop.Med.Hyg_83_266
Author(s) : Djenontin A , Chandre F , Dabire KR , Chabi J , N'Guessan R , Baldet T , Akogbeto M , Corbel V
Ref : American Journal of Tropical Medicine & Hygiene , 83 :266 , 2010
Abstract : The combined efficacy of a long-lasting insecticidal net (LLIN) and a carbamate-treated plastic sheeting (CTPS) or indoor residual spraying (IRS) for control of insecticide-resistant mosquitoes was evaluated in experimental huts in Burkina Faso. Anopheles gambiae from the area is resistant to pyrethroids and to a lesser extent, carbamates. Relatively low mortality rates were observed with the LLIN (44%), IRS (42%), and CTPS (52%), whereas both combinations killed significantly more mosquitoes (~70% for LLIN + CTPS and LLIN + IRS). Blood feeding by An. gambiae was uninhibited by IRS and CTPS compared with LLIN (43%), LLIN + CTPS (58%), and LLIN + IRS (56%). No evidence for selection of the kdr and ace-1(R) alleles was observed with the combinations, whereas a survival advantage of mosquitoes bearing the ace-1(R) mutation was observed with IRS and CTPS. The results suggest that the combination of the two interventions constitutes a potential tool for vector-resistance management.
ESTHER : Djenontin_2010_Am.J.Trop.Med.Hyg_83_266
PubMedSearch : Djenontin_2010_Am.J.Trop.Med.Hyg_83_266
PubMedID: 20682865

Title : Chlorfenapyr: a pyrrole insecticide for the control of pyrethroid or DDT resistant Anopheles gambiae (Diptera: Culicidae) mosquitoes - N'Guessan_2007_Acta.Trop_102_69
Author(s) : N'Guessan R , Boko P , Odjo A , Akogbeto M , Yates A , Rowland M
Ref : Acta Trop , 102 :69 , 2007
Abstract : Owing to the development and spread of pyrethroid resistance in Anopheles gambiae in Africa there is an urgent need to develop alternative insecticides to supplement the pyrethroids. Chlorfenapyr is a pyrrole insecticide first commercialized for the control of agricultural pests and termites. Performance against An. gambiae bearing kdr (pyrethroid and DDT resistance) or Ace-1(R) insensitive acetylcholinesterase (organophosphate and carbamate resistance) mechanisms was studied using a variety of adult bioassay tests including a simulated-experimental hut system (tunnel tests) that allows uninhibited mosquito behaviour/insecticide interactions. Strains resistant to pyrethroids and organophosphates showed no cross resistance to chlorfenapyr. In cone bioassays on treated netting the mortality of adult mosquitoes showed an unexpected curvilinear response, with highest mortality occurring at intermediate dosages. Adults expressed irritability to chlorfenapyr at higher dosages, which might explain the dosage-mortality trend. Toxic activity of chlorfenapyr was slow compared to conventional neurotoxic insecticides and additional mortality occurred between 24h and 72 h. In tunnel tests, the dosage-mortality trend showed a more typical sigmoid response and most mortality occurred during the first 24h. Mosquito penetration through the holed, treated netting showed only limited inhibition and blood-feeding was not inhibited. Mortality rates in the kdr strain exposed to chlorfenapyr treated netting in tunnel tests were much higher than with permethrin treated netting over the same 100-500 mg/m(2) dosage range. Chlorfenapyr has potential for malaria control in treated-net or residual spraying applications in areas where mosquitoes are pyrethroid resistant. For treated-net applications chlorfenapyr might be combined with pyrethroid as a mixture to provide personal protection as well as to give control of resistant mosquitoes.
ESTHER : N'Guessan_2007_Acta.Trop_102_69
PubMedSearch : N'Guessan_2007_Acta.Trop_102_69
PubMedID: 17466253

Title : Synergy between repellents and non-pyrethroid insecticides strongly extends the efficacy of treated nets against Anopheles gambiae - Pennetier_2007_Malar.J_6_38
Author(s) : Pennetier C , Corbel V , Boko P , Odjo A , N'Guessan R , Lapied B , Hougard JM
Ref : Malar J , 6 :38 , 2007
Abstract : BACKGROUND: To manage the kdr pyrethroid-resistance in Anopheline malaria vectors, new compounds or new strategies are urgently needed. Recently, mixing repellents (DEET) and a non-pyrethroid insecticide (propoxur) was shown to be as effective as deltamethrin, a standard pyrethroid, under laboratory conditions, because of a strong synergy between the two compounds. In the present study, the interactions between two repellents (DEET and KBR 3023) and a non-pyrethroid insecticide (pyrimiphos methyl or PM) on netting were investigated. The residual efficacy and the inhibition of blood feeding conferred by these mixtures were assessed against Anopheles gambiae mosquitoes.
METHODS: DEET and KBR 3023 were mixed with pyrimiphos methyl (PM), a organophosphate (OP) insecticide. The performance of mono- and bi-impregnated nets against adult mosquitoes was assessed using a miniaturized, experimental hut system (laboratory tunnel tests) that allows expression of behavioural responses to insecticide, particularly the mortality and blood feeding effects.
RESULTS: Both mixtures (PM+DEET and PM+KBR3023) induced 95% mortality for more than two months compared with less than one week for each compound used alone, then reflecting a strong synergy between the repellents and PM. A similar trend was observed with the blood feeding rates, which were significantly lower for the mixtures than for each component alone. CONCLUSION: Synergistic interactions between organophosphates and repellents may be of great interest for vector control as they may contribute to increase the residual life of impregnated materials and improve the control of pyrethroid-resistance mosquitoes. These results prompt the need to evaluate the efficacy of repellent/non-pyrethroid insecticide mixtures against field populations of An. gambiae showing high level of resistance to Ops and pyrethroids.
ESTHER : Pennetier_2007_Malar.J_6_38
PubMedSearch : Pennetier_2007_Malar.J_6_38
PubMedID: 17394646

Title : Evaluation of indoxacarb, an oxadiazine insecticide for the control of pyrethroid-resistant Anopheles gambiae (Diptera: Culicidae) - N'Guessan_2007_J.Med.Entomol_44_270
Author(s) : N'Guessan R , Corbel V , Bonnet J , Yates A , Asidi A , Boko P , Odjo A , Akogbeto M , Rowland M
Ref : Journal of Medical Entomology , 44 :270 , 2007
Abstract : Owing to the spread of pyrethroid resistance in Anopheles gambiae s.s. (Diptera: Culicidae) and other vector mosquitoes, there is an urgent need to develop alternative insecticides to supplement the pyrethroids for malaria control. Indoxacarb is an oxadiazine insecticide initially commercialized by DuPont for control of agricultural pests. Performance against An. gambiae bearing kdr (pyrethroid and DDT resistance) or Ace-1R insensitive acetylcholinesterase (organophosphate and carbamate resistance) mechanisms was studied using larval and adult bioassays and a simulated experimental hut system (tunnel tests) that allows fuller expression of the behavioral responses to insecticide. Larval and adult bioassays (topical application and cone tests on treated netting) showed a standard probit dosage-mortality response and no evidence of cross-resistance to the kdr and Ace-1R resistance mechanisms. Toxic activity was slow compared with standard insecticides and additional mortality was observed. Indoxacarb induced no excitorepellency in adults. In tunnel tests, indoxacarb induced no inhibition of mosquito penetration or blood feeding through the holed netting, but it induced delayed mortality over 24-96 h. There was > 90% mortality of the kdr strain on netting treated with the 500 mg/m2 dosage, whereas permethin at 500 mg/nm2 only killed 30% of this strain. A mixture of indoxacarb and pyrethroid showed neither synergism nor antagonism. The absence of cross-resistance to current insecticides indicates that indoxacarb has malaria vector control potential as larvicide or adulticide where mosquitoes are pyrethroid resistant.
ESTHER : N'Guessan_2007_J.Med.Entomol_44_270
PubMedSearch : N'Guessan_2007_J.Med.Entomol_44_270
PubMedID: 17427696

Title : Multiple insecticide resistance mechanisms in Anopheles gambiae and Culex quinquefasciatus from Benin, West Africa - Corbel_2007_Acta.Trop_101_207
Author(s) : Corbel V , N'Guessan R , Brengues C , Chandre F , Djogbenou L , Martin T , Akogbeto M , Hougard JM , Rowland M
Ref : Acta Trop , 101 :207 , 2007
Abstract : Because free-insecticide treated net distribution is planned in Benin (West Africa) during the next few years, we investigated the type, frequency and distribution of insecticide resistance mechanisms in Anopheles gambiae and Culex quinquefasciatus mosquitoes in four localities selected on the basis of contrasting agricultural practices, use of insecticides and environment. Bioassays with WHO diagnostic test kits were carried out using pyrethroid, carbamate, organophosphate and organochlorine insecticides. An. gambiae mosquitoes were identified to species and to M or S molecular forms using PCR techniques. Molecular and biochemical assays were carried out to identify kdr and Ace.1 mutations in individual mosquitoes and to detect any increase in the activity of enzymes typically involved in insecticide metabolism (oxidase, esterase and glutathion-S-transferases). WHO diagnostic tests showed high frequency of resistance in An. gambiae and Cx. quinquefasciatus to permethrin and DDT in three areas. This was consistent with the presence of target site insensitivity due to kdr mutation and to increased metabolism through enzymatic activity. Kdr was expressed in both M and S forms. However, less than 1% of An. gambiae or Cx. quiqnuefasciatus showed the presence of the Ace.1(R) mutation. Carbamate/OP resistance was present at higher frequency in Culex than in An. gambiae. Dieldrin resistance was present in both species at all four localities. A higher frequency of pyrethroid-resistance was found in An. gambiae mosquitoes collected in urban areas compared to those collected in rice growing areas. The expansion of vegetable growing within urban areas probably contributed to selection pressure on mosquitoes. The detection of multiple resistance mechanisms in both An. gambiae and Cx. quinquefasciatus in Benin may represent a threat for the efficacy of ITNs and other forms of vector control such as indoor residual spraying in the future.
ESTHER : Corbel_2007_Acta.Trop_101_207
PubMedSearch : Corbel_2007_Acta.Trop_101_207
PubMedID: 17359927

Title : Experimental hut evaluation of bednets treated with an organophosphate (chlorpyrifos-methyl) or a pyrethroid (lambdacyhalothrin) alone and in combination against insecticide-resistant Anopheles gambiae and Culex quinquefasciatus mosquitoes - Asidi_2005_Malar.J_4_25
Author(s) : Asidi AN , N'Guessan R , Koffi AA , Curtis CF , Hougard JM , Chandre F , Corbel V , Darriet F , Zaim M , Rowland MW
Ref : Malar J , 4 :25 , 2005
Abstract : BACKGROUND: Pyrethroid resistant mosquitoes are becoming increasingly common in parts of Africa. It is important to identify alternative insecticides which, if necessary, could be used to replace or supplement the pyrethroids for use on treated nets. Certain compounds of an earlier generation of insecticides, the organophosphates may have potential as net treatments.
METHODS: Comparative studies of chlorpyrifos-methyl (CM), an organophosphate with low mammalian toxicity, and lambdacyhalothrin (L), a pyrethroid, were conducted in experimental huts in Cote d'Ivoire, West Africa. Anopheles gambiae and Culex quinquefasciatus mosquitoes from the area are resistant to pyrethroids and organophosphates (kdr and insensitive acetylcholinesterase Ace.1R). Several treatments and application rates on intact or holed nets were evaluated, including single treatments, mixtures, and differential wall/ceiling treatments. RESULTS AND CONCLUSION: All of the treatments were effective in reducing blood feeding from sleepers under the nets and in killing both species of mosquito, despite the presence of the kdr and Ace.1R genes at high frequency. In most cases, the effects of the various treatments did not differ significantly. Five washes of the nets in soap solution did not reduce the impact of the insecticides on A. gambiae mortality, but did lead to an increase in blood feeding. The three combinations performed no differently from the single insecticide treatments, but the low dose mixture performed encouragingly well indicating that such combinations might be used for controlling insecticide resistant mosquitoes. Mortality of mosquitoes that carried both Ace.1R and Ace.1S genes did not differ significantly from mosquitoes that carried only Ace.1S genes on any of the treated nets, indicating that the Ace.1R allele does not confer effective resistance to chlorpyrifos-methyl under the realistic conditions of an experimental hut.
ESTHER : Asidi_2005_Malar.J_4_25
PubMedSearch : Asidi_2005_Malar.J_4_25
PubMedID: 15918909

Title : Experimental hut comparisons of nets treated with carbamate or pyrethroid insecticides, washed or unwashed, against pyrethroid-resistant mosquitoes - Asidi_2004_Med.Vet.Entomol_18_134
Author(s) : Asidi AN , N'Guessan R , Hutchinson RA , Traore-Lamizana M , Carnevale P , Curtis CF
Ref : Med Vet Entomol , 18 :134 , 2004
Abstract : The efficacy against mosquitoes (Diptera: Culicidae) of a bednet treated with carbamate insecticide [carbosulfan capsule suspension (CS) 200 mg/m(2)] was compared with four types of pyrethroid-treated nets in veranda-trap huts at Yaokoffikro near Bouake, Cote d'Ivoire, where the malaria vector Anopheles gambiae Giles carries the kdr gene (conferring pyrethroid resistance) at high frequency and Culex quinquefasciatus Say is also pyrethroid resistant. Pyrethroids compared were lambdacyhalothrin CS 18 mg/m(2), alphacypermethrin water dispersible granules (WG) 20 mg/m(2), deltamethrin 50 mg/m(2) (Permanet) and permethrin emulsifiable concentrate (EC) 500 mg/m(2). Insecticidal power and personal protection from mosquito bites were assessed before and after the nets were used for 8 months and hand washed five times in cold soapy water. Before washing, all treatments except permethrin significantly reduced blood-feeding and all had significant insecticidal activity against An. gambiae. The carbosulfan net gave significantly higher killing of An. gambiae than all pyrethroid treatments except the Permanet. Against Culex spp., carbosulfan was more insecticidal and gave a significantly better protective effect than any of the pyrethroid treatments. After washing, treated nets retained various degrees of efficacy against both mosquito genera - but least for the carbosulfan net. Washed nets with three types of pyrethroid treatment (alphacypermethrin, lambdacyhalothrin, permethrin) gave significantly higher mortality rates of Culex than in huts with the same pyrethroid-treated nets before washing. After five washes, the Permanet, which is sold as a long-lasting insecticidal product, performed no better than the other nets in our experimental conditions.
ESTHER : Asidi_2004_Med.Vet.Entomol_18_134
PubMedSearch : Asidi_2004_Med.Vet.Entomol_18_134
PubMedID: 15189238

Title : Efficacy of mosquito nets treated with insecticide mixtures or mosaics against insecticide resistant Anopheles gambiae and Culex quinquefasciatus (Diptera: Culicidae) in Cote d'Ivoire - Hougard_2003_Bull.Entomol.Res_93_491
Author(s) : Hougard JM , Corbel V , N'Guessan R , Darriet F , Chandre F , Akogbeto M , Baldet T , Guillet P , Carnevale P , Traore-Lamizana M
Ref : Bull Entomol Res , 93 :491 , 2003
Abstract : Only pyrethroid insecticides have so far been recommended for the treatment of mosquito nets for malaria control. Increasing resistance of malaria vectors to pyrethroids threatens to reduce the potency of this important method of vector control. Among the strategies proposed for resistance management is to use a pyrethroid and a non-pyrethroid insecticide in combination on the same mosquito net, either separately or as a mixture. Mixtures are particularly promising if there is potentiation between the two insecticides as this would make it possible to lower the dosage of each, as has been demonstrated under laboratory conditions for a mixture of bifenthrin (pyrethroid) and carbosulfan (carbamate). The effect of these types of treatment were compared in experimental huts on wild populations of Anopheles gambiae Giles and the nuisance mosquito Culex quinquefasciatus Say, both of which are multi-resistant. Four treatments were evaluated in experimental huts over six months: the recommended dosage of 50 mg m(-2) bifenthrin, 300 mg m(-2) carbosulfan, a mosaic of 300 mg m(-2) carbosulfan on the ceiling and 50 mg m(-2) bifenthrin on the sides, and a mixture of 6.25 mg m(-2) carbosulfan and 25 mg m(-2) bifenthrin. The mixture and mosaic treatments did not differ significantly in effectiveness from carbosulfan and bifenthrin alone against anophelines in terms of deterrency, induced exophily, blood feeding inhibition and overall mortality, but were more effective than in earlier tests with deltamethrin. These results are considered encouraging, as the combination of different classes of insecticides might be a potential tool for resistance management. The mixture might have an advantage in terms of lower cost and toxicity.
ESTHER : Hougard_2003_Bull.Entomol.Res_93_491
PubMedSearch : Hougard_2003_Bull.Entomol.Res_93_491
PubMedID: 14704095

Title : Resistance to carbosulfan in Anopheles gambiae from Ivory Coast, based on reduced sensitivity of acetylcholinesterase - N'Guessan_2003_Med.Vet.Entomol_17_19
Author(s) : N'Guessan R , Darriet F , Guillet P , Carnevale P , Traore-Lamizana M , Corbel V , Koffi AA , Chandre F
Ref : Med Vet Entomol , 17 :19 , 2003
Abstract : Resistance to carbosulfan, a carbamate insecticide, was detected in field populations of the malaria vector mosquito Anopheles gambiae Giles (Diptera: Culicidae) from two ecologically contrasted localities near Bouake, Ivory Coast: rural M'be with predominantly M form of An. gambiae susceptible to pyrethroids; suburban Yaokoffikro with predominantly S form of An. gambiae highly resistant to pyrethroids (96% kdr). The discriminating concentration of 0.4% carbosulfan (i.e. double the LC100) was determined from bioassays with the susceptible An. gambiae Kisumu strain. Following exposure to the diagnostic dosage (0.4% carbosulfan for 1 h), mortality rates of female An. gambiae adults (reared from larvae collected from ricefields) were 62% and 29% of those from M'be and Yaokoffikro, respectively, 24 h post-exposure. Exposure for 3 min to netting impregnated with the operational dosage of carbosulfan 200 mg/m2 gave mortality rates of 88% of those from M'be and only 12.2% for Yaokoffikro. In each case the control untreated mortality rate was insignificant. Biochemical assays to detect possible resistance mechanism(s) revealed the presence of insensitive AChE in populations of An. gambiae at both localities, more prevalent in the S form at Yaokoffikro than in M form at M'be, as expected from bioassays results. Our study demonstrates the need to monitor carbamate resistance among populations of the An. gambiae complex in Africa, to determine its spread and anticipate vector control failure if these insecticides are employed.
ESTHER : N'Guessan_2003_Med.Vet.Entomol_17_19
PubMedSearch : N'Guessan_2003_Med.Vet.Entomol_17_19
PubMedID: 12680920

Title : Evidence for selection of insecticide resistance due to insensitive acetylcholinesterase by carbamate-treated nets in Anopheles gambiae s.s. (Diptera: Culicidae) from Cote d'Ivoire - Corbel_2003_J.Med.Entomol_40_985
Author(s) : Corbel V , Hougard JM , N'Guessan R , Chandre F
Ref : Journal of Medical Entomology , 40 :985 , 2003
Abstract : Pyrethroid-treated nets are an efficient tool for reducing malaria transmission and morbidity. The recent evolution of pyrethroid resistance in several Anopheles species represents a major threat for the future success of roll back malaria in Africa. The possible use of nonpyrethroid insecticides, such as carbamates, on nets is a promising alternative solution because these insecticides are effective against susceptible and pyrethroid-resistant populations of Anopheles and Culex mosquitoes. Unfortunately, carbamate resistance as a result of insensitive acetylcholinesterase has recently been detected in Anopheles gambiae s.s. populations from Cote d'Ivoire. Using biochemical assays on surviving Anopheles mosquitoes from an experimental hut trial, we showed evidence for selection for an insensitive acetylcholinesterase mechanism by carbamate impregnated bednets. However, no such selection has been found with nets treated with pyrethroid alone or pyrethroid/carbamate "two-in-one" -treated nets. Because pyrethroid-impregnated nets were suspected to select for the Kdr mutation in An. gambiae, we propose that use of two-in-one nets could be a promising alternative strategy for the management of insecticide resistance in malaria vectors.
ESTHER : Corbel_2003_J.Med.Entomol_40_985
PubMedSearch : Corbel_2003_J.Med.Entomol_40_985
PubMedID: 14765680